It’s a “controlled experiment” if there’s a sample which is used as a control. Whether that sample is under the control of the experimenter (or arises naturally) is a totally different issue:
http://en.wikipedia.org/wiki/Natural_experiment
http://en.wikipedia.org/wiki/Experiment#Controlled_experiments
Fair enough—the author has changed the wording of the main article in any case.
It’s a “controlled experiment” if there’s a sample which is used as a control. Whether that sample is under the control of the experimenter (or arises naturally) is a totally different issue:
http://en.wikipedia.org/wiki/Natural_experiment
http://en.wikipedia.org/wiki/Experiment#Controlled_experiments
Fair enough—the author has changed the wording of the main article in any case.